The last seven games of the Red Bulls’ regular season won’t just be about trying to reach the postseason. They’ll also be about planning for next season, and one of the most pivotal and expensive decisions they’ll have to make is regarding Designated Player Frank Rost and their troublesome goalkeeper situation.

A team that has enjoyed past and present U.S. National Team keepers Tony Meola, Tim Howard and Jonny Walker have struggled mightily to fill that role since Jon Conway’s departure. After Bouna Coundoul’s dip in form this season, they gambled big _ literally and figuratively _ on Rost, 38, MLS’ only DP keeper.

He’s coming off a 1-0 shutout at FC Dallas last Saturday, and was set to take the field tonight vs. Real Salt Lake. With a hefty $550,000 salary _ prorated for this season _ it’s incumbent that they choose wisely whether to pick up his hefty option for next season or move forward with somebody cheaper or younger or both.

“He played great (Saturday). You saw the way he dealt with corners and free kicks, he didn’t miss one,’’ said coach Hans Backe. “Yes, we were a little worried about the quad injury, but it was no problem. And I think the best thing about him is that he is very loud. He communicated with the back four. He was massive.’’

But so is the risk. Already committed to Thierry Henry and Rafa Marquez for over $10 million for next season, the Red Bulls’ salary cap figures to be squeezed even without the Rost; but they have to figure if the towering 6-foot-5 Bundesliga veteran is an injury risk.

He had a shutout in his debut, but then gave up eight goals in 2 ½ games, forced out of a 3-0 loss at Real Salt Lake with a quad injury. Now _ after missing three straight games before Saturday’s return _ he’ll face that same team tonight.

“It was the worst case that could happen. I can’t change what happened: It is what it is,’’ said Rost, brushing off criticism after the injury. “I played 20 years at a high level and I want to bring that here. I’m not interested in what others are saying and talking about. I’m a good keeper on a high level. This is the first time I have any muscle injury in my career. All I can do is fight and play with heart.”

Earlier this season, GM Erik Soler told the Post that part of his job would be to determine a successor for Rost, and part of the German’s duty is to help tutor him.

“My personal view on it is I will try what I can to keep him for next year,’’ Soler told the Post. “Parallel with that we need to figure out who is going to be the goalkeeper that will pick up the glow after him, so he can learn out of his experience. Personally I think he’s a great keeper.’’

Coundoul is in the Top 10 all-time in MLS in both save percentage (4th at 76%) and goals-against-average (6th at 1.13). But the 27-year-old Senegal National Team starter saw his form dip this year after the shocking firing of highly-regarded goalkeeping coach Des McAleenan.

McAleenan had tutored Howard and Conway, and coached Meola and Walker as well, often considered the finest goalkeeping coach in MLS. He was quickly scooped up by Al Hilal in Saudi Arabia, the most successful club in all of Asia. Without him, the Red Bulls’ keepers have struggled.

They also have Alex Horwath, who has a shutout in his only league appearance this season; and pool keeper Chris Konopka, a local product who grew up in Toms River (NJ) and played at Providence. With Coundoul making $178,000, it seems difficult to afford both he and Rost next year.

“He’s good off his line, good with balls in the air. When he needed to catch a ball, he was there. When he needed to punch a ball out he was there. He was strong, he commands his box,” center back Tim Ream said of Rost.

“For us, it makes our job easier; and his communication, we knew when he was going to come off his line and get a through ball and we knew when he was staying back. He helped us with runners through. Just overall he has a pretty positive approach.’’